Windows Server 2008
Windows Server 2008, codenamed "Longhorn Server", is the seventh major version of the Windows NT operating system produced by Microsoft to be released under the Windows Server brand name. It was released to manufacturing on February 4, 2008, and generally to retail on February 27, 2008. Derived from Windows Vista, Windows Server 2008 is the successor to Windows Server 2003 R2 and the predecessor to Windows Server 2008 R2. It removed support for computers without ACPI, and is the first version that includes Hyper-V.
Source: Wikipedia
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